When speech recognition is to be performed using an instrument such as a car-navigation device, a smartphone and the like, such an instrument not necessarily has sufficient hardware resources. For that reason, there is a client-server speech-recognition system in which, instead of internally executing all of speech recognition of a speech, the instrument transmits its speech data to an external server followed by receiving a result of speech recognition performed by the server. Note that the “client” herein means an instrument at user's hand, such as a car-navigation device, a smartphone, and the like. Consequently, even at the client, it becomes possible to utilize large-vocabulary based speech recognition. However, a recognition word specific to the client, a proper noun only found in an address book of the user, and the like are not necessarily recognizable by the server.
As a measure therefor, in Patent Document 1, there is disclosed a technique of not only merely performing speech recognition by the server followed by receiving the result by the client, but also performing, depending on a speech, speech recognition both by the client and by the server followed by differently indicating both of the recognition results or selecting either one of the results. Specifically, in Patent Document 1, there is described that, when either one of the recognition results by the client or the server is to be selected, a higher one in acoustic likelihood is selected.